A bus bar electrically connects, for example, terminals of electrodes of a battery module of a secondary battery.
A bus bar that connects terminals of electrodes, through which a large current flows, needs to have a predetermined thickness in order to decrease electrical resistance. On the other hand, the bus bar needs to have flexibility for maintaining the precision in position relative to the terminals to which the bus bar is connected, thereby to adapt to distortion due to a shock or heat from the outside, and swelling of the cells.
A generally used bus bar is configured such that two connection portions are provided on a plate member having such a plate thickness as to be able to suppress electrical resistance, and an arcuate spring-like portion is provided between the two termination connection portions. Thereby, the generally used bus bar keeps electrical resistance low, and has a certain degree of flexibility.
The above-described bus bar can absorb, by deformation of the arcuate spring-like portion, a shock in one direction connecting the two connection portions. However, the above bus bar has low flexibility against a shock in other directions. In addition, in the above bus bar, by reducing the plate thickness, the flexibility can be improved but, conversely, it becomes difficult to keep electrical resistance low.
The object of the embodiments is to provide a bus bar which keeps electric resistance low (i.e. have low resistance) and has a sufficient flexibility, and a battery module.